Guideless resilient androgynous serial port docking mechanism

ABSTRACT

The Guideless Resilient Androgynous Serial Port (GRASP) mechanism provides an androgynous mechanical and electrical interface that can be tailored to the meet the requirements of a given application. Each mechanism is equipped with physical connections (spring pins) for both power and data transmission between modules.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation in Part of U.S. application Ser. No. 16/953,420 filed Nov. 20, 2020, which is a Continuation of U.S. application Ser. No. 16/740,546 filed Jan. 13, 2020 now U.S. patent Ser. No. 10/882,645 issued Jan. 5, 2021, both of which claim priority to U.S. Provisional Application 62/791,918 filed Jan. 14, 2019, and all of which are hereby incorporated herein by reference.

GOVERNMENT CONTRACT

The invention was made with government support with United States Government Agency, Defense Advanced Research Projects Agency under Contracts D16PC00182 and D17PC00307. The Government has certain rights in the invention.

BACKGROUND OF THE INVENTION

The SYNERGEO modular spacecraft platform concepts provide a unique challenge for assembly interface design, requiring an androgynous, retractable mechanical connection, physical connections for both data and power transmission, and a layout exhibiting at least 90° rotational symmetry to support multiple assembly orientations.

The research effort to develop a functional assembly interface design started with existing concepts and a literature review of past spacecraft docking port designs. Until the turn of the century, spacecraft docking port design was focused on human-rated technology to enable missions to orbiting research and observation platforms such as Spacelab, MIR and the ISS. This information provided some useful insight into the various strategies for spacecraft approach and docking, and the underlying technologies that enable these large, retractable and androgynous docking solutions provided a useful starting reference for the development of the GRASP. Shifting focus to the realm of small satellites, there have been some interesting developments in the last 15 years, but domestic efforts have largely eschewed androgyny and the ability to retract in favor of emulating the classical probe-drogue port design, which is time-tested and proven in both space and atmosphere. Publicly available information on recent domestic developments include the non-androgynous Mechanical Docking System used on Orbital Express, the SPHERES androgynous but asymmetric Universal Docking Port (UDP) demonstrated successfully on the ISS, the Autonomous Satellite Docking System (ASDS) developed and demonstrated by Michigan Aerospace, the AMODS electro-magnetic docking system under development at the US Naval Academy, and Velcro pads, which are non-androgynous and unreliable in structural applications.

All these docking ports fail to meet SYNERGEO requirements for symmetric androgyny. International efforts in the realm of small satellite docking ports have yielded several concepts; two of the relevant concepts are a semi-androgynous docking interface under development at the University of Padova, Italy, and the port utilized in the German iBOSS effort, which is a potential option for the modular spacecraft concept. The port under development at University of Padova is an innovative concept that can switch between probe and drogue functions as needed and uses a central spring-loaded plunger to supply the force necessary to maintain secure docking.

SUMMARY OF THE INVENTION

The Guideless Resilient Androgynous Serial Port (GRASP) assembly interface uses a novel mechanism to provide an androgynous, selectable-preload structural connection which supports a variety of secondary interfaces that can be tailored to meet application requirements (electrical connections, thermal load transmission, among others), and to which specific alignment feature arrays can be added if so desired. Developed under the DARPA SYNERGEO program (Phase I #D16PC00182 and Phase II #D17PC00307), assembly interfaces comprised of a multi-mechanism array and a single mechanism have been developed. Initial GRASP mechanism prototype designs are equipped with integrated physical connections (spring pins) for both power and data transmission between modules. The more recent single-point GRASP assembly interface design moved to a modular interface, in which the electrical connections (spring pin arrays) and alignment features have become modular add-ons to the mechanism providing the structural connection, to better accommodate the diversity of interface requirements posed by various applications and markets.

Numerous other advantages and features of the invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims, and from the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee. A fuller understanding of the foregoing may be had by reference to the accompanying drawings, wherein:

FIG. 1 is a test apparatus equipped with four Generic Resilient Androgynous Serial Port (GRASP) v1 prototypes (corners), wherein the GRASP mechanisms can be configured to perform interface alignment during docking; this apparatus is used to demonstrate a multi-point GRASP assembly interface that exhibits 90° rotational symmetry normal to the contact plane;

FIGS. 2A-2B illustrate a multi-point (2A) and single-point (2B) GRASP assembly interface concepts, the GRASP spring pin arrays are designed to enable connections between identical assembly interfaces;

FIG. 3 illustrates the multi-point GRASP array designed for SYNERGEO, which allows a pair of module interfaces to mate successfully in four orientations, each established by rotating one of the two bodies by 90° increments about the +z axis of its interface. In the example above, the passive body is held stationary while the active is rotated;

FIGS. 4A-4D are illustrations of a GRASP breadboard prototype;

FIG. 5 is an exploded view of the GRASP breadboard prototype equipped with an integrated ratchet;

FIGS. 6A-6C are illustrated views of the GRASP breadboard prototype, shown in the ‘active’ configuration (docking screw fully extended); this first prototype is equipped with a ratchet to enable androgyny, with the teeth integrated into the docking nut;

FIG. 7 illustrates GRASP breadboard prototypes; the mechanism to the left integrates a ratchet into the docking nut, while the mechanism to the right uses a needle roller clutch (one-way bearing) to achieve the desired one-way freewheel behavior;

FIG. 8 is a GRASP v1 prototype illustration;

FIGS. 9A-9C are detailed view of the GRASP v1 prototype, shown in the ‘passive’ configuration (docking screw fully retracted); this prototype uses a needle roller clutch to enable androgyny;

FIGS. 10A-10D show the docking process between two GRASP mechanisms, shown in 4 steps; the active mechanism is denoted by A, while B is the passive mechanism;

FIG. 11 illustrate a conceptual GRASP v2 mechanism contact surface features;

FIG. 12 illustrates a conceptual GRASP v2 drivetrain arrangement (CONOPS sensor package not shown);

FIGS. 13A-13D show detailed views of the GRASP v2 prototype concept, to be used for the SYNERGEO single-point GRASP interface, shown in the ‘active’ configuration (docking screw fully extended); this prototype uses a needle roller clutch to enable androgyny;

FIG. 14 is an exploded perspective view of a docking nut system for use with GRASP mechanism in accordance with another embodiment of the invention;

FIG. 15 is an assembled view of the docking nut system from FIG. 14;

FIG. 16 is a bottom view of the assembled view of the docking nut system in its housing in accordance with an embodiment of the invention;

FIG. 17 is a bottom view of a GRASP mechanism installed into a surface plate;

FIG. 18 is perspective view of a GRASP mechanism installed into a base plate;

FIG. 19 is a cross section view of the GRASP mechanism from FIG. 18;

FIGS. 20A and 20B are sectional views of the GRASP mechanism from FIG. 18 illustrating two of the three pucks rested in cavities;

FIG. 21 is an exploded view of a connector in accordance with one embodiment of the invention;

FIG. 22 is an assembled view of the connector from FIG. 21;

FIG. 23 is an alterative connector in accordance with an embodiment of the invention; and

FIG. 24 is a cross section view of a GRASP mechanism with a floating docking nut system coupled to a secondary surface.

DESCRIPTION OF THE INVENTION

The apparatuses shown in FIGS. 1 and 2A are an equally-spaced array of 4 GRASP v1 mechanisms 100 mounted to a structural plate 50 built to simulate a face of a SYNERGEO spacecraft, while FIG. 2B shows a GRASP assembly interface having a single GRASP mechanism and equipped with 4 identical, symmetrically arranged groups of alignment features and electrical connections. However, it is easily contemplated that the GRASP mechanism can be used to dock two opposing surfaces and are not limited or restricted to the use on a spacecraft. The GRASP mechanism may thus be used both in space and terrestrial applications. These include, but are not limited to, underwater, on land, or in flight, by both aircraft and spacecraft, used in robotic applications, end effectors, and tool-changers.

The multi-point interface electrical array includes 24 discrete pairs of high-current connections for power transmission (6 per mechanism) and eighty discrete pairs of low-power connections for data transmission (20 per mechanism). The large number of low-power pins enable a tailored approach to communications from module to module and throughout the modular spacecraft platform based on payload requirements for security, bandwidth, or noise. Secure mating between modules equipped with a 4-point interface can be accomplished using as few as two diagonally opposed mechanisms, providing a high level of redundancy in comparison to existing solutions. The complement of electrical connections, location of electrical connection groups, and housing geometry selected for the multi-point SYNERGEO interface are one of many possible solutions and are readily altered or customized to meet the needs of other applications.

Note that 90° rotational symmetry at the interface is typically a customer requirement and this can change depending on the requirements or guidelines, illustrated in FIG. 3, is a requirement for SYNERGEO that has been satisfied with both a multi-GRASP array and a single GRASP mechanism. FIG. 3 shows the multi-point GRASP array designed for SYNERGEO, which allows a pair of module interfaces to mate successfully in four orientations, each established by rotating one of the two bodies by 90° about the +z axis of its interface. In the example above, the passive body is held stationary while the active is rotated. The modular and customizable features of the GRASP mechanism 100 and interface concept provide the spacecraft builder a variety of approaches to satisfying structural, electrical, and morphological constraints particular to a given application.

At a fundamental level, the GRASP mechanism 100 provides a mechanical connection through a bolted joint. The novelty of GRASP is the androgyny of the mechanism; a GRASP in the ‘passive’ configuration, FIGS. 4A-4D, has the docking screw fully retracted and acts as the nut, while a GRASP in the ‘active’ configuration, FIGS. 6A-6C, has the docking screw fully extended and acts as the bolt. This androgyny is made possible by allowing the docking nut to rotate (freewheel) about its cylindrical axis in only one direction.

As provided in greater detail for FIGS. 4A-6C, the GRASP mechanism 100 has a base plate 105 having an outward facing surface 107 that would serve as the connection surface to another GRASP mechanism. The base plate 105 also has an inward facing surface 109. The base plate 105 has numerous channels bored through to service as conduits 110 for the various supplies or signals, power, water, electrical, data etc. These include various spring pins and pin targets 116, some of which may be referred to commonly as pogo pins used in electrical connector applications. An array 115 of these pins would be connected on the inward facing surface 109 over the conduits 110 and extend to the connection surface such that when two GRASP mechanisms were connected a full signal and supply connection would be made (the various conduit tubing connecting to the array is not shown). Multiple arrays may be employed as needed or required by design.

The GRASP mechanism 100 has a housing unit 120 secured to the base plate 105 over an opening 125 defined in the base plate 105. The outward facing surface 107 may also include an indented surface 130 surrounding the opening 125 to assist in the alignment. The indented surface 130 may have a cylindrical outer wall profile or it may be tapered in a truncated cone (FIG. 9) towards the opening 125 to help guide the docking screw into the opening. The housing unit 120 is defined by a lower housing 135 that is either secured to the inward facing surface 109 of the base plate 105 or the lower housing 135 may be molded with the base plate 105 as a single unitary structure. The lower housing 135 includes a lip 140 surrounding the opening 125 with a ridge 142 extending to a circular surface wall 144. Adjacent a portion of the circular surface wall 144 is a channel cut out 146.

Positioned against the ridge 142 and over the opening 125 is a docking nut 150. The docking nut 150 has a body portion 152 that includes a threaded interior surface 154 with an exterior lower ratchet toothed section 156. The exterior lower ratchet toothed section 156 rotatably sits against the ridge 142 within the circular surface wall 144. A pawl 160 and spring 162 are positioned by a pawl pin 163 in the channel cut out 146 to engage the ratchet toothed section allowing rotation of the docking nut 150 in only a single direction. A docking screw 165 is threaded into the docking nut 150.

Secured to the lower housing is an upper housing 170 used to secure the docking nut and pawl in position. The upper housing 170 includes a bore 172 sized to receive the docking screw and the body portion 152 of the docking nut 150.

The docking screw 165 has an interior channel 167 keyed to receive a profiled driveshaft 180 that when inserted and rotated in either direction will rotate the docking screw 165. There also exists in an alternative concept a driveshaft that is a machined feature of the docking screw, and a concept in which the docking screw has a splined or hex-cut head which is driven by matching features internal to the final drive of a transmission, or matching features machined into the rotor or stator of the motor, for example in a direct drive. The docking screw 165 may further have an extended flat top or bullet nose 169 used to locate into the docking nut of the other mechanism during connection.

The driveshaft 180 is meshed to a main gear 185 further meshed to spur gear(s) 187 and driven by a motor 190. The top 182 of the drive shaft 180 is rotatably positioned against a bearing 184 mounted to a mounting plate 192. Posts 195 are secured between the mounting plate 192 and the base plate 105 to secure the mounting plate to the base plate with the motor 190 mounted between the two plates as well.

A variety of existing technologies, (e.g. ratchet, one-way bearing, sprag clutch), can be used in the GRASP mechanism to achieve this one-way freewheel motion. The GRASP breadboard mechanism 100 shown in FIGS. 4-7 implements a simple ratchet with teeth integrated into the docking nut and a pawl mounted to the mechanism base plate. Another iteration 200, shown on the right of FIG. 7, replaced the ratchet teeth and pawl of the GRASP 100 mechanism with a flange, and used a one-way bearing (needle roller clutch) known to achieve the desired rotational limit. This approach is applied to the GRASP v1 prototype, FIGS. 8-9C, and in the single-point GRASP interface depicted in FIGS. 11-13.

Referring now to FIG. 9A-9C the GRASP mechanism 200 is designed similarly to the GRASP mechanism 100, but as mentioned employs a needle roller clutch 205 to restrict rotation of the docking nut to a single direction.

Docking screw motion in the v1 and v2 prototypes is powered by a COTS brushless DC micro-motor (“BLDC motor”) which transmits torque to the driveshaft via a parallel-output transmission. The motor is sized to provide the torque required at the driveshaft to generate the mechanical preload required by the application and maintain sufficient margin. A variety of sensors and mechanism monitoring strategies are used to monitor performance during actuation and verify that joint mechanical preload requirements have been met. Other drivetrain arrangements can also be developed to transmit the required torque to the docking screw or driveshaft. The driveshaft can also be redesigned to transmit torque directly to the docking screw. One could even directly drive the docking screw if so desired. Once can also use a stepper, AC, or DC motor to power the mechanism—the current design was selected based on SYNERGEO requirements.

The docking process between two GRASP breadboard mechanisms, representing one ‘corner’ of the 4-point SYNERGEO interface, is shown in FIGS. 10A-10D. Due to the androgynous design of the docking mechanism, either module can be assigned the active role in the operation. In this series of images, the active port is designated by 100A or A, while 100B or B is the passive port.

In the first step, APPROACH, a servicing spacecraft will use its robotic manipulators to present the incoming module for docking to the platform in a predetermined orientation, ensuring the correct docking ports are aligned.

In step 2, the motor of active port A will activate, advancing its docking screw such that it threads through the ratchet nut until the head of the docking screw contacts the ratchet nut, after which the ratchet nut will freewheel and the docking screw with the nut will then continue to turn clockwise. In the various embodiments of the mechanisms discussed herein, the docking screw during its initial rotations with rotate through a stationary docking nut. When the docking screw is fully extending through the docking nut and the head of the screw comes into contact with the docking nut, continuous rotation of the docking screw causes a torque on the docking nut such that the nut will begin to turn with the rotation of the screw. In the embodiment of the ratchet/pawl, the teeth and pawl are configured to prevent rotation in one direction but allow slippage when the torque from the screw is pressed into the nut and rotation is continued. In the embodiment of the needle roller clutch it is the configuration of the clutch to prevent rotation in one direction and allow rotational slippage to avoid over-torqueing. These work perfectly in the current GRASP mechanisms.

During the third step, ALIGN, the tip of the mechanism A docking screw will be protruding from the side of the spacecraft, and the screw+nut combination will continue to freely rotate clockwise as the tip of the docking screw is brought into contact with the mechanism B alignment cone. The tip of the screw will traverse the mechanism B alignment cone, correcting any misalignment between the mechanisms so docking screw A engages the threads in the mechanism B ratchet sleeve. During cone traversal, the rotating motion of the screw tip helps reduce contact friction at the screw/alignment cone interface.

Once aligned, the continuously rotating docking screw+nut combination of mechanism A will engage the threads of the mechanism B docking nut, and the torque provided by the motor actuating mechanism A will tighten the bolted joint and end when the target interface preload is achieved. It is during this step that power and data connections are made.

The transition of the spacecraft module design from a multi-point interface to a single-point interface required the addition of separate alignment feature and electrical connection groups to meet the SYNERGEO 90° rotational symmetry requirement. The single-point interface provides 8 discrete pairs of data connections, intended to be used to provide two gigabit ethernet connections, but with the ability to be repurposed as desired. The alignment features complement of electrical connections, and base plate geometry chosen for the single-point SYNERGEO interface are one of many possible solutions, and are readily altered or customized to meet the needs of other applications. The difference between the v1 prototype mechanism used for early testing and the GRASP v2 concept is illustrated in FIG. 2.

The single-point concept meets the 90° rotational symmetry requirement and provides fine alignment during docking using a static array of conventional probe+drogue alignment features. While the static alignment probes have the potential to shrink the available volume for the spacecraft modules, the mass and complexity savings of moving to a single-point interface prove an acceptable trade.

During exploration of the single-point concept, it was determined in an alternative embodiment to provide a GRASP mechanism with modular electrical connection modules so that the electrical interface can be updated as the station architecture concept evolves, or customized to meet the needs of other applications.

In FIGS. 11-13D, concept designs of a GRASP mechanism 300 are shown, with ample space available for the electrical connection modules. FIG. 11 depicts a contact surface of the interface with screw extended, while FIG. 12 illustrates the drivetrain and an early mounting bracket, designed to preserve alignment between the driveshaft and the docking screw throughout the range of travel.

As illustrated the conceptual GRASP mechanism 300 has an X shaped base plate 305 having an outward facing surface 306 that would serve as the connection or contact surface to another GRASP mechanism. The base plate 305 also has an inward facing surface 309. The base plate 305 has an alignment probe 307 with corresponding alignment cones 310 that help align two GRASP mechanisms. The probes 307 when approaching the alignment cones on a second GRASP mechanism will ride the cones to the center aligning the two mechanisms together.

The GRASP mechanism 300 has one way bearing mount 320 secured to the base plate 305 over an opening 325 defined in the base plate 305. The outward facing surface 306 may also include an indented surface 327 surrounding the opening 325 to assist in the alignment. The indented surface 327 may have a cylindrical outer wall profile or it may be tapered in a truncated cone towards the opening 325 to help guide the docking screw into the opening. The one-way bearing mount 320 houses the needle roller clutch 330 and the docking nut 350. As noted above, the docking nut 350 has a body portion that includes a threaded interior surface. A docking screw 360 is threaded into the docking nut 350.

The docking screw 360 has an interior channel 365 keyed to receive a profiled driveshaft 380 that when inserted and rotated by an output shaft 382 in either direction will rotate the docking screw 360. The docking screw 360 may further have an extended flat top or bullet nose 367 used to locate into the docking nut of the other mechanism during connection.

The driveshaft 380 is controlled by a BLDC motor 385 with a parallel output transmission 390 and field director 395. Posts 397 are secured between the base plate 305 and the transmission housing. Lastly, the base plate 305 includes interface mounts 308 permitting the GRASP mechanism 300 to be secured to a surface of a spacecraft.

As defined by the drawings herein, there is provided a first GRASP mechanism for a docking system and for use with a second GRASP mechanism similarly configured, or a similarly configured interface prepared to dock with a GRASP mechanism. Each of the GRASP mechanisms include:

(a) a base plate having an opening bored through, wherein the base plate has an outward facing connection surface configured to position against a second base plate of the second GRASP mechanism when the first and second GRASP mechanisms are docked together;

(b) a two-piece housing unit secured to the base plate over the opening, the two-piece housing unit defined by a lower housing and an upper housing, the lower housing includes a lip surrounding the opening and a ridge extending from the lip to a circular surface wall extending away from the base plate;

(c) a docking nut being positioned against the ridge and over the opening, the docking nut having a threaded interior surface;

(d) a rotational restriction mechanism being positioned against the docking nut within the circular surface wall to engage the docking nut and configured to permit rotation of the docking nut in a single direction;

(e) a docking screw threaded into the docking nut, the docking screw having an interior channel keyed to receive a drive shaft; and

(f) a motor mechanism configured to rotate the docking screw via the drive shaft.

Based on the above, the docking screw has a screw length SL configured to extend through the docking nut and through the base plate when the docking screw is in an extension position (FIG. 6B) and the docking nut has a nut length NL configured to define a receiving space 207 (FIG. 9C) below the docking screw 165 when the docking screw is un-extended through the docking nut whereby the receiving space 207 of the docking nut is further configured to receive a portion of a second docking screw in the extension position when the first and second GRASP mechanisms are docked together (FIG. 10D).

In various embodiments, the rotational restriction mechanism is configured to (i) allow one-way slip rotation of the docking nut when the docking screw is fully inserted through the docking nut such that a head of the docking screw is in contact with the docking nut; and (ii) prevent the counter rotation of the docking nut, such as when the docking screw is inserted and rotated into the receiving space of a second GRASP mechanism during a docking of first and second GRASP mechanisms.

The rotational restriction mechanisms can either be employed by a lower ratchet toothed section on the docking nut rotatably and a pawl mechanism positioned to engage the exterior lower ratchet toothed section to permit rotation of the docking nut in a single direction. Alternatively, the rotational restriction mechanism can be defined by having a needle roller clutch positioned in the lower housing and configured to permit rotation of the docking nut in a single direction.

In another embodiment, the GRASP mechanism has a base plate with an X shape and wherein the outward facing connection surface include one or more alignment probes and one or more alignment indented cones, wherein when the first and second GRASP mechanisms are being docked together, the one or more alignment probes are configured to insert and slide within corresponding one or more of the alignment indented cones to adjust a position of the first and second GRASP mechanisms.

As provided herein, the GRASP mechanism is typically utilized as part of a docking system configured to dock two surfaces together. The docking system includes at least a pair of opposing generic resilient androgynous serial port (GRASP) mechanisms. Each of the GRASP mechanisms being positioned on the separate surfaces and which connect to each other to dock the separate surfaces together. The docking system further includes a mounting platform configured on a side of separate surfaces, and wherein the sides of the separate surfaces being configured for docking to each other. Each surface is designed to have at least one GRASP mechanism secured to the mounting platform. The GRASP mechanisms are defined each to include: (i) a base plate having an opening bored through, wherein the base plate has an outward facing connection surface configured to position against a second base plate of the opposing GRASP mechanism when the separate surfaces are docked together; (ii) a docking nut being positioned over the opening, the docking nut having a threaded interior surface; (iii) a rotational restriction mechanism being positioned against the docking nut to engage the docking nut and configured to permit rotation of the docking nut in a single direction; (iv) a docking screw threaded into the docking nut; (v) a motor mechanism configured to thread the docking screw through the docking nut; and (vi) wherein the docking screw has a screw length configured to extend through the docking nut and through the base plate when the docking screw is in an extension position and wherein the docking nut has a nut length configured to define a receiving space below the docking screw when the docking screw is un-extended through the docking nut whereby the receiving space of the docking nut is further configured to receive a portion of a second docking screw in the extension position when the opposing GRASP mechanisms are docking together.

In another embodiment illustrated in FIG. 14, there is shown a docking nut system 400 that can be embodied within an improved float system 500 that fits into the GRASP system. The docking nut system 400 includes a central bushing 405 with a groove 410 annularly positioned around the outside of the central bushing 405. The groove 410 is designed to seat a bushing damper 415. Positioned within the central bushing 405 is a one-way bearing 420 that secures the docking nut 425. Extending outwardly from around the central bushing 405 are three pucks 430. Each puck is held to the central bushing by a dowl 435 inserted into a surface hole 440 on the bushing. Each puck further includes a puck damper 445. While not shown in FIG. 14, FIG. 15 shows the assembled docking nut system 400 with a dog end 450 integral to the docking nut 425. When assembled, the docking screw pawl 451 can engage the docking nut dog end to avoid stripping of the screw.

Referring now also to FIG. 16, the docking nut system 400 is shown installed into a GRASP housing 460 that is then secured to the overall GRASP system 470, FIG. 17. As now seen when installed in FIGS. 18-20, similar reference numbers are used to describe similar components.

The float system is designed to provide limited 6 degree-of-freedom movement around the central axis and about the x and y planes. Each rotation would be about 3 degrees to each side of the axis or plane, ensuring the docking screw is able to compensate for imperfect alignment when it contacts the target interface threads. In the depicted version, motion is damped via compressible puck dampers 445, and the limits of motion are set by the dimensions of the respective cavities 447 in which the bushing and pucks are located, thus a less or more degree of freedom movement can be achieved.

As mentioned, the float system design provides limited 6 degree-of-freedom compliance this is to ensure the power connectors are able to compensate for imperfect interface alignment during the GRASP interface docking process. These connectors 500, illustrated in FIGS. 21-23, includes both flat contacts 505 and at least one alignment contact 510. The outward facing contact surface 512 of the alignment contact 510 includes an indented surface 514 centered on the contact. The indented surface 514 being configured to compensate for relative misalignment between mating connectors when an alignment pin 520 of the mating connector is in contact with the indented surface and the connectors 500 are brought together. The alignment pin 520 is identical to the other spring pins 525 in the connector, but protrudes further from the connector face 545 defined by the connector housing 540 such that it contacts the mating connector's alignment contact and travels partly along the indented surface before the other spring pins connect with their target contacts. The connector housing 540 includes a pair of grooves 550 along the outside of the housing to receive housing dampers 555. The connector housing 540 fits within a housing sleeve 560. The connector housing 540 secures into a housing base 565 with coupling connectors 570 situated in the housing base 565 to connect a connector with a pin. The assembled power connector 500 is shown in FIG. 22

In the depicted version, motion is damped via housing dampers 555, and the limits of motion are set by the dimensions of the cavity in which the power connector assembly resides, and there is only one alignment contact. It is trivial to change the array such that all pin contacts have an indented surface, as in 4-conductor, 4-channel connector 580 shown in FIG. 23.

This float system is designed such that the array of electrical connectors in a GRASP assembly interface can make correct, reliable contact if the gross rotational alignment of the GRASP assembly interface, of which they are a member, is within 1 degree of perfect rotational alignment.

As shown in FIG. 24 the GRASP Assembly with the improved float system 400 and improved connectors 500 can dock with a basic receiver assembly 600 that is equipped with threaded hole rather than a GRASP mechanism. The threaded hole may also be replaced with a commercially-available separation nut to make the dummy interface ‘redundant to release’.

While particular elements, embodiments, and applications of the present invention have been shown and described, it is understood that the invention is not limited thereto because modifications may be made by those skilled in the art, particularly in light of the foregoing teaching. It is therefore contemplated by the appended claims to cover such modifications and incorporate those features which come within the spirit and scope of the invention. 

We claim:
 1. A guideless resilient androgynous serial port (GRASP) mechanism for use with a secondary docking system for docking two separate components together, the GRASP mechanism comprising: a base plate having an opening bored through, wherein the base plate has an outward facing connection surface configured to position against the secondary docking system when the GRASP mechanism and the secondary docking system are docked together; a docking nut system positioned over the opening in the base plate, the docking nut system having: a central bushing having a one-way bearing positioned within the central bushing to secure a docking nut therein, the central bushing further includes three holes equally spaced around an outside perimeter of the central bushing, three pucks, separately secured to one of the three holes, each puck includes a puck damper positioned around an outside thereof, and a docking nut positioned over the opening and secured within the one-way bearing, the docking nut having a threaded interior surface; a housing secured to the base plate over the opening, the housing having a central opening to receiving the central bushing and having three offset cavities defined to separately accommodate the three pucks, each of the three offset cavities being configured to provide a pre-determined degree of movement of the pucks about each central axis configured into each puck; a docking screw threaded into the docking nut, the docking screw having an interior channel keyed to receive a drive shaft; a motor mechanism configured to rotate the docking screw via the drive shaft; and wherein the docking screw has a screw length configured to extend through the docking nut and through the base plate when the docking screw is in an extension position to receive into a receiving portion of a secondary docking system when the GRASP mechanism and the secondary docking system are docked together.
 2. The GRASP mechanism of claim 1, wherein the central bushing includes a groove annularly positioned around an outside surface of the central bushing, the groove being sized to seat a bushing damper.
 3. The GRASP mechanism of claim 1, wherein the base plate of the GRASP mechanism include a plurality of channels bored through and configured as conduits for signal ports and signal and data pins to provide electrical and data communications between the GRASP mechanism and the secondary docking system when secured and connected.
 4. The GRASP mechanism of claim 2, wherein the outward facing connection surface of the base plate includes an indented surface surrounding the opening, the indented surface being configured to assist in the alignment when the GRASP mechanism and the secondary docking system are secured together.
 5. The GRASP mechanism of claim 3, wherein the docking screw has a pawl configured to engage a dog end extending from the docking end to prevent over rotation of the screw.
 6. The GRASP mechanism of claim 1, wherein the pre-determined degree of movement is a 3 degree-of-freedom movement about each axis configured for a total of 6 degrees about each axis.
 7. The GRASP mechanism of claim 1 further comprising at least one connector configured to mate with a connector situated on the secondary docking system, and wherein the connectors are defined to provide electrical and data communications between the GRASP mechanism and the secondary docking system when secured and connected.
 8. The GRASP mechanism of claim 7, wherein each of the connectors include: at least one alignment pin and at least one alignment contact, wherein the at least one alignment contact includes an indented surface configured to compensate for relative misalignment between mating connectors when an alignment pin of the mating connector is in contact with the indented surface, a connector housing securing the at least one alignment pin and the at least one alignment contact, the connector housing including a pair of grooves along an outside of the housing to receive housing dampers, and a housing sleeve situated over the connector housing and secured to a housing base.
 9. The GRASP mechanism of claim 8 further comprising at least one flat contact and at least one connector pin.
 10. A guideless resilient androgynous serial port (GRASP) mechanism for a spacecraft docking system and for use with a secondary docking system, wherein the GRASP mechanism comprising: a base plate having an opening bored through, wherein the base plate has an outward facing connection surface configured to position against the secondary docking system when the GRASP mechanism and the secondary docking system are docked together; a docking nut system positioned over the opening in the base plate, the docking nut system having: a central bushing positioned within the central bushing to secure a docking nut therein, the central bushing further includes three holes equally spaced around an outside perimeter of the central bushing, three pucks, separately secured to one of the three holes, each puck includes a puck damper positioned around an outside thereof, and a docking nut positioned over the opening and secured within the central bushing, the docking nut having a threaded interior surface; a housing secured to the base plate over the opening, the housing having a central opening to receiving the central bushing and having three offset cavities defined to separately accommodate the three pucks, each of the three offset cavities being configured to provide a pre-determined degree of movement of the pucks about each central axis configured into each puck; a docking screw threaded into the docking nut, the docking screw having an interior channel keyed to receive a drive shaft; a motor mechanism configured to rotate the docking screw via the drive shaft; and wherein the docking screw has a screw length configured to extend through the docking nut and through the base plate when the docking screw is in an extension position to receive into a receiving portion of a secondary docking system when the GRASP mechanism and the secondary docking system are docked together.
 11. The GRASP mechanism of claim 10, wherein the central bushing includes a groove annularly positioned around an outside surface of the central bushing, the groove being sized to seat a bushing damper.
 12. The GRASP mechanism of claim 10, wherein the base plate of the GRASP mechanism include a plurality of channels bored through and configured as conduits for signal ports and signal and data pins to provide electrical and data communications between the GRASP mechanism and the secondary docking system when secured and connected.
 13. The GRASP mechanism of claim 10, wherein the outward facing connection surface of the base plate includes an indented surface surrounding the opening, the indented surface being configured to assist in the alignment when the GRASP mechanism and the secondary docking system are secured together.
 14. The GRASP mechanism of claim 10, wherein the docking screw has a pawl configured to engage a dog end extending from the docking end to prevent over rotation of the screw.
 15. The GRASP mechanism of claim 10, wherein the pre-determined degree of movement is a 3 degree-of-freedom movement about each axis configured for a total of 6 degrees about each axis.
 16. The GRASP mechanism of claim 10 further comprising at least one connector configured to mate with a connector situated on the secondary docking system, and wherein the connectors are defined to provide electrical and data communications between the GRASP mechanism and the secondary docking system when secured and connected.
 17. The GRASP mechanism of claim 16, wherein each of the connectors include: at least one alignment pin and at least one alignment contact, wherein the at least one alignment contact includes an indented surface configured to compensate for relative misalignment between mating connectors when an alignment pin of the mating connector is in contact with the indented surface, a connector housing securing the at least one alignment pin and the at least one alignment contact, the connector housing including a pair of grooves along an outside of the housing to receive housing dampers, and a housing sleeve situated over the connector housing and secured to a housing base.
 18. The GRASP mechanism of claim 17 further comprising at least one flat contact and at least one connector pin. 